Doors using key or combination locks to control access to other keys and/or other controlled assets or areas have been in existence in one form or another for centuries if not millennia. Currently, it is typical for such doors to include a latch with an extendable tongue mounted to the door such that the tongue catches behind a strike on the frame of the door when extended. Latches of this type usually feature a spring biased tongue member with a ramped edge (on the side facing the door opening) so that the door can be slammed or closed even when the tongue is extended and the latch is locked. Such locks/latches are, therefore, commonly referred to as “slam latches” in the art. More recently, doorjambs have also been fitted with electrically disengageable hinged strikes. These hinged strikes are spring biased to their normal position and are maintained in that position by a strike holding mechanism that can be deactivated by the plunger of a solenoid as long as the solenoid is activated by an electrical current. While this hinged strike holding mechanism is deactivated, the hinged strike is free to rotate outward such that it no longer serves to engage and retain the tongue of a latch mounted to the door. This, in turn, allows the door to be opened even though the tongue of its latch has not been unlocked/withdrawn. Usually electronic means actuated by a keyboard and/or card are used to electrically trigger the solenoid so that it deactivates the hinged strike holding mechanism and thereby allows the hinged strike to rotate outward, releasing the door to be opened.
Dual access systems of the type described above have several advantages. First, selected individuals can be allowed access to a closed structure or lock box without possessing a key as long as they possess the requisite means. Such means can take the form of a keyboard personal identification number (a “PIN”), a card, a fingerprint, an eye print, and/or any other means necessary to deactivate the strike for its latch. Second, the use of a key provides a simple non-electrical means for opening the lock when electricity is absent or temporarily unavailable. Third, such means (e.g. in the form of a “master key”) simultaneously provide those in overall authority with easy access to the contents of the lock box or secured structure. Fourth, such systems work very well for security purposes. Electronic systems retain a memory of those accessing contents or the interior of structures via electronic means, while those authorized and possessing keys are limited in number and known.
Despite their advantages, such systems also have a notable disadvantage: the hinged strike holding mechanism can jam. This is particularly a problem if the door or door jamb is warped or when too much material is stuffed into a lock box or secured structure prior to closing its door. This can lead to binding forces on the strike holding mechanism preventing it from unlocking and releasing the door.
The jamming problem associated with hinged strikes is exacerbated by another factor. Most secured doors of the type discussed herein are provided with a sensor/signal generator so that it can easily be determined whether the door is open or closed. Such signal generators typically use a system (such as a “Reed switch”) where one part of the sensor is placed in the frame and another placed opposite in the door. When the door is open and the parts are no longer adjacent, this state is indicated. Likewise, when the door is closed and the sensor parts are adjacent, this state is indicated. Since doors fitted with slam latches are normally locked when closed, an indication that the door is closed will normally be taken as a signal that it is secured (and its strike holding mechanism properly engaged), even when this is not the case. Thus, there is a substantial need for a disengageable strike that will avoid the jamming features discussed above. There is also a substantial need for a system that will indicate not only that a door is closed, but that its disengageable strike is engaged and in a position where it will securely engage the slam latch for a secured enclosure.